#include <queue>
using namespace std;

int N;
int grid[500][500];
bool visited[500][500];
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
int target;

int bfs(int sx, int sy, int D) {
    queue<pair<int,int>> q;
    q.push({sx, sy});
    visited[sx][sy] = true;
    int cnt = 1;
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();
        for (int d = 0; d < 4; d++) {
            int nx = x + dx[d];
            int ny = y + dy[d];
            if (nx < 0 || nx >= N || ny < 0 || ny >= N) continue;
            if (visited[nx][ny]) continue;
            int diff = grid[x][y] - grid[nx][ny];
            if (diff < 0) diff = -diff;
            if (diff > D) continue;
            visited[nx][ny] = true;
            cnt++;
            q.push({nx, ny});
        }
    }
    return cnt;
}

bool check(int D) {
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
            visited[i][j] = false;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            if (!visited[i][j]) {
                if (bfs(i, j, D) >= target) return true;
            }
        }
    }
    return false;
}

int main() {
    cin >> N;
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
            cin >> grid[i][j];

    target = (N * N + 1) / 2;

    int lo = 0, hi = 1000000;
    while (lo < hi) {
        int mid = (lo + hi) / 2;
        if (check(mid)) {
            hi = mid;
        } else {
            lo = mid + 1;
        }
    }

    cout << lo << endl;
    return 0;
}